//每页显示条目，默认0
@Input() rows: number = 0;
//显示分页按钮数量，默认5
@Input() pageLinkSize: number = 5;
//点击按钮后向父组件发送事件
@Output() onPageChange: EventEmitter<any> = new EventEmitter();
//调整每页显示条目数量的下拉菜单
@Input() rowsPerPageOptions: number[];
//定义分页按钮
pageLinks: number[];
_totalRecords: number = 0;
_first: number = 0;
//数据总数
@Input() get totalRecords(): number {
 return this._totalRecords;
}
set totalRecords(val: number) {
 this._totalRecords = val;
 this.updatePageLinks();
}
//高亮按钮位置
@Input() get first(): number {
 return this._first;
}
set first(val: number) {
 this._first = val;
 this.updatePageLinks();
}

 //获取一共多少页
getPageCount() {
 return Math.ceil(this.totalRecords / this.rows) || 1;
}

//获取当前页,0为第一页
getPage(): number {
 return Math.floor(this.first / this.rows);
}

//是否为第一页
isFirstPage(): boolean {
 return this.getPage() === 0;
}

//是否为最后一页
isLastPage(): boolean {
 return this.getPage() === this.getPageCount() - 1;
}

//确定当先需要显示的起始分页和结束分页
calculatePageLinkBoundaries() {
 let numberOfPages = this.getPageCount();
 let visiblePages = Math.min(this.pageLinkSize, numberOfPages);
 let start = Math.max(0, Math.ceil(this.getPage() - (visiblePages / 2)));
 let end = Math.min(numberOfPages - 1, start + visiblePages - 1);

 const delta = this.pageLinkSize - (end - start + 1);
 start = Math.max(0, start - delta);
 return [start, end];
}

//更新需要显示的分页条目
updatePageLinks(): void {
 this.pageLinks = [];
 let boundaries = this.calculatePageLinkBoundaries;
 const start = boundaries[0];
 const end = boundaries[1];
 for (let i = start; i <= end; i++) {
  this.pageLinks.push(i + 1);
 }
}

//点击分页
changePage(p: number, event) {
 var pageCount = this.getPageCount();
 if (p > 0 && p < pageCount) {
  this.first = this.rows * p;
  const state = {
   page: p,
   first: this.first,
   rows: this.rows,
   pageCount: pageCount
  };
  this.updatePageLinks();

  this.onPageChange.emit(state);
 }
 if (event) {
  event.preventDefault();
 }
}

//第一页
changePageToFirst(event){
 this.changePage(0,event);
}

//上一页
changePageToPrev(event){
 this.changePage(this.getPage() - 1,event);
}

//下一页
changePageToNext(event){
 this.changePage(this.getPage() + 1,event);
}

//最后一页
changePageToLast(event){
 this.changePage(this.getPageCount() - 1,event);
}

//通过下拉菜单更改每页显示数量
onRppChange(event){
 this.rows = this.rowsPerPageOptions[event.target.selectedIndex];
 this.changePageToFirst(event);
}